Insecticidal Controlled Atmosphere for Management of Sweetpotato Whitefly Progress Report –August 1995
Date 9/1/95
Title of Project Insecticidal Controlled Atmosphere for Management of Silverleaf
Whitefly
Institution where work is being conducted University of Massachusetts
Amount of Endowment Grant $14,174
Covering Period 2/95 to 1/96
Anticipated Date of Project Completion/Final Report 1/96
Individual(s) Conducting Project:
(List Project Leader First)
Dr. Susan S. Han - Title Assistant Professor
Telephone Number 413-545-5228
Insecticidal Controlled Atmosphere forManagement of Silverleaf Whitefly
Susan S. Han
University of Massachusetts
- A. Project Objectives:
- The main objective of the study is to investigate the potential of use of controlled atmospheres for control ofsilverleaf whitefly (Bemisia argentifoii) on floricultural crops. Controlled atmospheres (CA) for long-term storage of
edible crops has been extensively investigated. The method refers to changes in the composition of the air surrounding
the commodity and generally involves reduction of oxygen and/or elevation of carbon dioxide. In recent years, the use
of elevated CO2 or reduced O2 atmospheres to induce sublethal and lethal effects on insects has provided an excellent
alternative to chemical fumigation for quarantine treatment of imported edible crops. The time required for 100%
mortality of an insect depends on the species, its developmental stage, and the temperature and atmospheric
composition during the treatment. Commodities differ in their susceptibility to CA and the recommendations for the level
of tolerance to reduced O2 and/or elevated CO2 varies (Ke and Kader, 1992). Floricultural crops can tolerate higher
levels of CO2 than most edible crops, perhaps due to the higher surface to volume ratio (Joyce and Reid, 1985).
- Results from my laboratory have demonstrated that reduced O2 treatments (<2 PPM O2), are effective againstboth greenhouse and silverleaf whitefly. All adult greenhouse whitefly were killed with a 2-hr exposure to the low-02
treatment whereas other stages of whitefly were killed with treatments of < 8 hr. These studies were conducted in a
20'C controlled-temperature room. Studies on Caribbean fruit fly (Benschoter, 1987) and western flower thrips (Reid,
personal communication) have demonstrated that increasing the temperature increases the insecticidal effect of the
treatment. In a preliminary experiment where eggs of greenhouse whitefly were exposed to the low-O2 conditions at
30'C, we observed that a 1O' increase in temperature significantly increased the lethal effect of the CA treatment. The
objectives of this project are to determine the length of time required to kill adults, eggs, nymphs and pupae of silverleaf
whitefly at various temperatures. In addition, we will evaluate the level of tolerance to low-O2 atmospheres of various
crops that are susceptible to whitefly infestation.
- B. Results to Date:
- We have investigated the insecticidal effects of reduced O2 treatment in a 3O’C chamber. Excised poinsettialeaves were collected from the greenhouse at the University of Massachusetts at Amherst. Leaves were then placed in
vials containing water followed by treatment with a constant flow of air (control) or with factory-mixed nitrogen gas
(containing < 2 PPM O2).
Following the gas treatment,
leaves were maintained in a
controlled environment growth
chamber with 12 hr of light
(17 +/- 3 umol*m-2*s-1)
provided by cool-white
fluorescent lamps. Except for
the pupal stage, the
percentage of whitefly that
were killed by the treatment
was tabulated. In the case of
pupae, the percentage of
pupae that had emerged into
adults was calculated. Of the
four stages (adults, nymphs,
eggs, and pupae), the adult stage was most sensitive to the CA treatment with 100% mortality occurring after an
exposure time of < 2 hr at 20'C or 30'C. In contrast, eggs were most resistant to the treatment. After a 4 or 8 hr
treatment with low-O2 at 20'C, 10% and 80%, respectively, of the eggs failed to hatch. Results from the 30'C studies
are not conclusive and further studies will be conducted. Sufficient control of the nymphal and pupal stage whitefly
required 8 hrs at 20'C or 4 hr at 30'C. The short-time, high-temperature conditions shall increase the potential for use
of this technique for disinfestation of whitefly on a wide range of crops.
- C. Future Plans Covered by the Endowment Grant:
- We will continue our investigations by examining the insecticidal effects of low O2 on silverleaf whitefly at othertemperatures as stated in the proposal. In addition, we will expose various species of annuals to the reduced-O2
environment in order to determine the tolerance levels of the crops to the treatment.
- D. Anticipated Benefits for Floral Industry:
- The proposed method of reduced-O2 insecticidal CA would provide the greenhouse industry with anenvironmentally-safe way of controlling the spread of whitefly through infested plant materials. The use of this technique
can be integrated into an IPM program. Practice of such an approach would drastically reduce the amount of
hazardous pesticides used, and would increase profitability to the greenhouse industry by reducing pesticide costs and
increasing the quality of the product.
